The objective of the research is to better understand the perception of complex auditory signals. While previous research has concentrated on simple stimuli such as sinusoids or noise bursts, the aim of the present research is to study the ability to discriminate changes in the power spectra of broadband acoustic stimuli. The goal is to use the knowledge we have already acquired about the simpler stimuli and apply it to the perception of these more complex stimuli. Specifically, three areas are scheduled for investigation: 1) the prediction problem--how can the detectability of complex spectral changes be predicted from the detectability of simpler spectral changes? 2) speech-like stimuli--does the detection of spectral change differ for harmonic and inharmonic complexes? 3) dynamic spectra--how does time variation in the spectra affect the ability to detect spectral change? Understanding the perception of complex auditory stimuli will promote the understanding of the relationship between peripheral auditory processes and more complex central processes such as the perception of speech. It will contribute some of the basic information needed to provide a rational basis for diagnosis and treatment of auditory impairments.